Device and method for adjusting a setpoint deceleration of a vehicle

ABSTRACT

Arrangement having a braking system for a vehicle, which, when a brake pedal is depressed, generates a corresponding braking effect, and having an operating device for setting a desired deceleration which is in an operative connection with an accelerator pedal, wherein, when the accelerator pedal is released, the braking system brakes the vehicle corresponding to the set desired deceleration.

[0001] The invention relates to an arrangement and a method for setting a desired deceleration of a vehicle while the accelerator pedal and the brake pedal are not operated.

[0002] In vehicles, particularly passenger cars and trucks, the accelerator pedal and the brake pedal are used for accelerating the vehicle and holding the driving speed, and decelerating the vehicle respectively. In certain traffic situations, the driver is forced to constantly change between operating the accelerator pedal and operating the brake pedal. This particularly applies to lines of traffic, especially on turnpikes, where a so-called accordion effect may occur. It is uncomfortable and tiring for the driver to constantly have to place the right foot between the accelerator pedal and the brake pedal. Such a traffic situation tempts drivers of automatic-transmission vehicles to “drive with both feet”; that is, the right foot is on the accelerator pedal while the left foot is on the brake pedal. This may lead to a constant operation of the brake and a resulting increased wearing of the brake and to an increased gasoline consumption because the engine and the brake continuously counteract one another.

[0003] It is an object of the present invention to provide an arrangement and a method which improve the comfort and the safety when driving a vehicle.

[0004] This object is achieved by means of the characteristics of the claims.

[0005] The invention is based on the idea of controlling the driving speed of a vehicle by operating or releasing the accelerator, in which case a desired deceleration can be set by means of an operating device, by which desired deceleration the vehicle is braked when the accelerator pedal is released. This adjustable desired deceleration is preferably greater than the inherent deceleration which occurs in the case of vehicles during the releasing of the accelerator in that the engine does not supply any driving power. This applies to vehicles with a manual transmission as well as to vehicles with an automatic transmission, which only have a low drag momentum when the accelerator is released, that is, a low inherent deceleration.

[0006] In particular, the invention can be used in combination with existing braking systems, also in combination with devices for controlling the driving speed, such as cruise controls and the ACC (automatic clutch control ? translator). In particular, the invention can be used in combination with power braking systems which, independently of the control by the driver, are capable of building up a wheel-individual brake pressure at all wheels, for example, the DSC (? translator). The invention can also be used in the case of braking systems with an automatic brake intervention by means of a hydraulic unit or a controllable brake power assist unit, as, for example, in the ACC operation.

[0007] In the following, the invention will be explained in detail by means of embodiments and the drawings.

[0008]FIG. 1 is a schematic representation of a preferred embodiment of the invention; and

[0009]FIG. 2 is a view of an embodiment of the arrangement of an operating device.

[0010] The embodiment of the invention illustrated in FIG. 1 is a preferred embodiment, the invention being usable in an identical manner in other braking systems. The embodiment of FIG. 1 illustrates a hydraulic braking system with a brake pedal 1, a brake power assist unit 2, a tandem master brake cylinder 3, a hydraulic unit 10, as well as wheel brakes 11, 12, 13, 14 for the four wheels of a vehicle. The hydraulic unit 10 has a control unit 20. An operating device 19 for setting a desired deceleration is connected with the control unit 20. In the illustrated example, the control unit 20 is also connected with a control unit 16 which receives an electrical signal from a brake light switch 15 arranged at the brake pedal 1 and is used for controlling brake lights 17, 18. In addition, the control unit 20 is connected with rotational wheel speed sensors 22, 23, 24, 25 which detect the rotational speed of the individual wheels.

[0011] During the driver-operated braking, force is exercised on the tandem master brake cylinder 3 by means of the brake pedal 1 using the assisting function of the brake power assist unit 2. As a result, a pressure is generated in the tandem master brake cylinder 3, which is propagated by way of brake lines 4, 5, 6, 7, 8, 9, through the hydraulic unit 10 to the wheel brakes 11, 12, 13, 14. By means of this brake pressure, the driver sets his desired vehicle deceleration. The movement of the brake pedal results in the generating of an electric signal in the brake light switch 15 which either directly or by way of an intermediately connected control unit 16 controls the brake lights 17, 18.

[0012] In certain traffic situations, the driver is forced to constantly change between the operation of the accelerator pedal and the brake pedal. In such cases, the driver can be relieved by the operating device 19 which makes it possible for him, after the releasing of the accelerator pedal, to set a braking effect exceeding the inherent deceleration of the vehicle without operating the brake pedal. Analogous to the functionality of an automatic braking intervention for the ACC, the braking intervention can take place by means of a suitable hydraulic unit 10: The electric signal supplied by the operating device 19 is detected by the control unit 20 of the hydraulic unit 10 and is converted to a desired deceleration value or desired pressure value. The hydraulic unit 10 takes in the brake fluid from a fluid reservoir 21 and builds up the required brake pressure in the wheel brakes 11, 12, 13, 14 until the actual deceleration corresponds to the desired value or the driver's intent. The amount of the vehicle deceleration can be derived from the signals of the rotational wheel speed sensors 22, 23, 24, 25. As an alternative, the actual deceleration can be detected by means of a longitudinal acceleration sensor (not shown). The occurring wheel brake pressures are either measured directly by means of suitable sensors or are estimated by way of a hydraulic model by means of the control times of the valves installed in the hydraulic unit 10 and the return pump.

[0013] The operating device designed according to ergonomic aspects is to be positioned such that it permits an intuitive fatigue-free operation by the driver without requiring the driver to look. Any operation by the driver results in a controlling of the brake lights 17, 18, optionally with the intermediate connection of a separate control unit 16.

[0014] The operating device 19 according to the invention is in an operative connection with the accelerator pedal 26, whereby the desired deceleration and the corresponding superimposed hydraulic intervention for operating the brakes will start only when the driver releases the accelerator pedal; that is, when the accelerator pedal is no longer operated and has returned into the initial position. The accelerator pedal position is detected by means of a pedal value generator 27 and the respective signal is emitted to the control unit 20.

[0015] The superimposed hydraulic intervention is terminated as soon as the driver operates the accelerator pedal again or as soon as the driver operates the brake pedal. Likewise, the hydraulic intervention is terminated when the operating device 19 is no longer operated.

[0016]FIG. 2 illustrates a preferred embodiment in which the operating device 19 in the form of a knurling wheel is arranged on the vehicle steering wheel such that an operation can be implemented by means of the thumb. This arrangement has the advantage that a reaching-around movement by means of the hand is not required and the operation can take place without looking. This knurling wheel has a self-restoring construction; that is, as soon as the thumb is removed from the knurling wheel, the latter automatically moves back and the superimposed hydraulic intervention is terminated.

[0017] The self-restoring of the knurling wheel takes place, for example, by way of an integrated spring device; that is, when the operating device is operated, a spring tension is built up which, when the knurling wheel is released, moves it back into the initial position.

[0018] As an alternative, the operating device 19 may be constructed in the form of a steering drop arm or in the form of a sensor surface which preferably emits a pressure-dependent signal.

[0019] The present invention can be expanded by the following changes or supplements. For example, the desired deceleration can be limited to a so-called comfort braking range which is known from ACC systems.

[0020] The braking system can be equipped with a pressure-maintaining function when the vehicle is stopped, preferably shortly before the vehicle stoppage, the deceleration control being changed to a pressure control. In addition, the wheel brake pressure may be shut in while the vehicle is stopped as long as the operating device is operated. This particularly has the advantage that, in the case of automatic transmission vehicles, the vehicle will not start rolling when the operating device is not yet operated.

[0021] In a preferred embodiment of the invention, not only a constant desired deceleration is set by means of the operating device, but the braking takes place as a function of the vehicle speed or of the lateral acceleration and the speed at which the operating device is operated, with desired dynamics or a desired progression of the pressure buildup curve.

[0022] Furthermore, the arrangement has a learning algorithm which permits a vehicle-adaptive dead-time control and progression.

[0023] The invention can particularly used in combination with a cruise control, the operating device 19 preferably being able to replace the “minus key” present in the case of a cruise control.

[0024] According to another preferred embodiment of the invention, in combination with a cruise control and/or an ACC system, the accelerator pedal can be used as a foot support, in which case, when an increased force feedback is exercised, the entire pedal travel is available for the accelerator pedal.

[0025] The invention improves the comfort and the safety when driving a vehicle and, in particular, permits a more relaxed driving in lines of traffic, particularly on turnpikes, which driving is not tiring because of the fact the fewer changes are required between the accelerator pedal and the brake pedal. In addition, it permits an expansion of the cruise control function and the construction of an accelerator pedal as a foot support.

[0026] Translation of FIG. 1: Translation of FIG. 1: AVHL exhaust valve rear left AVHR exhaust valve rear right AVVL exhaust valve front left AVVR exhaust valve front right DK damping chamber EVHL intake valve rear left EVHR intake valve rear right EVVL intake valve front left EVVR intake valve front right HA rear axle (hydraulic connection) HL wheel brake rear left HR wheel brake rear right HSV high-pressure (resistant) shift valve PD pulsation damper SK accumulator chamber sRFP self-priming return pump USV change-over valve VA front axle (hydraulic connection) VL wheel brake front left VR wheel brake front right Steuergerät control unit 

1. Arrangement having a braking system for a vehicle, which, when a brake pedal (1) is depressed, generates a corresponding braking effect, and having an operating device (19) for setting a desired deceleration which is in an operative connection with an accelerator pedal, wherein, when the accelerator pedal is released, the braking system brakes the vehicle corresponding to the set desired deceleration.
 2. Arrangement according to claim 1, wherein the operating device (19) has an adjusting wheel and is preferably arranged at the steering wheel or shifting knob of the vehicle or has a steering drop arm.
 3. Arrangement according to claim 1 or 2, wherein the braking system has a hydraulic unit (10) or a controllable brake power assist unit with a control unit (20), the operating device (19) supplying a desired value, preferably an electric signal, which the control unit (20) converts to a corresponding desired deceleration.
 4. Arrangement according to one of the preceding claims, having a device (22, 23, 24, 25) for detecting an actual deceleration of the vehicle and a comparator which compares the desired deceleration with the actual deceleration and, as a function of the result of the comparison, readjusts the brake pressure.
 5. Arrangement according to one of the preceding claims, having brake lights (17, 18) which are controlled directly or preferably by way of a second control unit (16) when operating the operating device (19).
 6. Arrangement according to one of the preceding claims, having a device for deactivating the desired deceleration when the brake pedal (1) is operated, or the accelerator pedal is operated again.
 7. Arrangement according to one of the preceding claims, having a device for limiting the setting range for the desired deceleration.
 8. Arrangement according to one the preceding claims, having a device for changing from a controlling of a vehicle deceleration to a controlling of a brake pressure, preferably as a function of a vehicle speed, particularly preferably at a vehicle speed which is lower than 15 km/h.
 9. Arrangement according to one of the preceding claims, having a device for maintaining a brake pressure when the vehicle is stopped, while operating the operating unit (19).
 10. Arrangement according to one of the preceding claims, having a device for storing at least one buildup curve respectively for the brake pressure as a function of a parameter, preferably a vehicle speed and/or a lateral acceleration of the vehicle and/or a speed at which the operating unit (19) is operated, the buildup curve corresponding to an adjustable desired deceleration.
 11. Arrangement according to one of the preceding claims, having a device for detecting a vehicle-specific buildup curve for the brake pressure.
 12. Arrangement according to one of the preceding claims, having a device for controlling the speed, preferably a cruise control, the operating unit (19) simultaneously forming a setting device for the cruise control.
 13. Arrangement according to one of the preceding claims, wherein, in a settable operating mode, the accelerator pedal has a limited pedal travel and can be used as a foot support, and wherein, the entire pedal travel is available by overcoming a defined force feedback.
 14. Method of setting a desired deceleration of a vehicle by means of an arrangement having the above-mentioned claims. 